The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A fuel system for a spark ignition direct injection (SIDI) engine may include a low-pressure fuel pump and a high-pressure fuel pump. The low-pressure fuel pump pumps fuel from a fuel tank to a low-pressure fuel line. The high-pressure fuel pump pumps fuel from the low-pressure fuel line to a high-pressure fuel line and/or fuel rail. Fuel injectors on the SIDI engine receive fuel at a high-pressure from the fuel rail. The fuel injectors directly inject fuel into combustion chambers of cylinders of the SIDI engine. This is different than a conventional multi-point fuel injection that includes injecting fuel into an intake tract or cylinder port.
Direct injection enables stratified fuel-charged combustion, which can provide improved fuel efficiency, reduced emissions and increased power output during normal engine operating temperatures (e.g., approximately 90° C.). Emissions output of a SIDI engine is generally greater during a cold engine start when operating at the normal engine operating temperatures. During a cold engine start (e.g., engine operating temperature of less than approximately 50° C.), fuel is injected in the combustion chambers and can impinge on top surfaces of pistons and on cylinder walls. This can prevent a complete combustion of the injected fuel, as the fuel on the top of the pistons and on the cylinder walls may not be fully ignited during ignition strokes. As a result, an increased amount of particulate may be generated during a combustion cycle and exhausted from the SIDI engine to an exhaust system.